High quality waveform monitors are commonly used for viewing and analyzing television signals, and they generally permit the user to view expanded portions of the television signal being monitored on the displays of the associated video waveform monitors. This enables the user to observe in great detail any part of the waveform being analyzed.
Present day waveform monitors use the horizontal position control of the instrument to select the portion of the waveform to be displayed. However, for several reasons the use of the horizontal position control for this purpose can be confusing. First of all, when using the horizontal position control to select the portion of the waveform to be displayed in expanded form, the user must know and remember the location of the selected portion of the waveform with respect to time. Secondly, the user must be able to recognize the selected portion of the waveform in the expanded format when he sees it, which often necessitates switching back and forth between the expanded and non-expanded sweeps. Consequently, it would be desirable to provide an improved method and apparatus which would avoid the necessity of switching back and forth between the expanded and non-expanded sweeps when selecting a particular portion of a waveform to be observed on the screen of the monitor and thus facilitate the use of the expanded sweep feature of the analyzer.